1. Field of the Invention
The invention relates to an effort coupling device for effort coupling between at least two piloting members of an aircraft comprising a piloting device equipped, for each flying member of the aircraft, with two such piloting members connected (by a completely mechanical kinematic chain or at least partly electrically) to this flying member, so that the aircraft can be piloted simultaneously by two people: a captain (or pilot) and a copilot.
Throughout the text, the term “piloting” and its derivatives denote, unless otherwise stated, the flying of an aircraft by at least one human pilot operating at least one piloting member such as a stick, handle, rudder bar, pedal, etc., connected to at least one flying member such as a control surface or a throttle control of the aircraft. Furthermore, the term “effort” is employed to denote equally well a torque or a force, according to the arrangement on which this effort is exerted (torque if it involves a rotation or force if it involves a translation).
2. Description of the Related Art
When an aircraft is to be piloted simultaneously by a pilot and a copilot, it is known to connect the piloting members or sticks of each of the two pilots to one another so that each stick moves in a manner servo-coupled to the other stick and so that each pilot can feel on his stick the effort exerted by the other pilot on his own stick. Traditionally, this effort coupling between the piloting members is carried out by a set of rods or cables mechanically connecting the two piloting members.
However, when the piloting members are of electrical or electronic type, it is necessary to simulate the behaviour of traditional mechanical sticks, for example by means of electric motors. From the document U.S. Pat. No. 5,291,113 there is known a piloting device having a coupling device realising the coupling of the displacements and the forces applied to the sticks of the pilot and the copilot. This piloting device has for each piloting member an operating handle connected to an effort sensor (in the form of a torque sensor) and a position sensor. Each torque sensor delivers a signal representing the torque exerted/felt by the pilot (and the copilot, respectively) on the operating handle. From the position signal delivered by the position sensor and an effort feedback value formed of the sum of the torque signals, a summer forms a torque error which is then applied to an electronic controller which delivers an appropriate control electric current to an electric motor in order to correct this torque error and modify the torque felt by the pilot (and the copilot, respectively).
Such an effort coupling device has the disadvantage of degrading the effort sensations of the pilot, on simulating a connection comparable to a rigid rod between the piloting members of the pilot and the copilot. Such a rod is normally accompanied, in mechanical systems, by devices which separate the sticks of the pilots when the effort generated by one on the other exceeds a predetermined limit. Such a “disconnection” is not achieved in the coupling device of the prior art and a limitation of the efforts is achieved only when the coupled efforts of the pilot and the copilot lead to saturation of the electric current supplied to the motor. In this case, the effort supplied by the motor against the effort of the pilot is constant and no longer enables the latter to feel his position with respect to the overall travel of the stick. Likewise, if effort variation laws such as sensations similar to surpassable notches or stops (for example vibrations induced by a stick vibrator for tactile alerting of a situation close to stalling) were provided as a function of the position, these are “erased” by the saturation of the control of the electric motor.